This invention relates to multi-speed planetary transmissions and, more particularly, to multi-speed planetary transmissions having three planetary gearsets and six torque-transmitting mechanisms to provide at least seven forward speed ratios and one reverse speed ratio.
Automatic shifting power transmissions are currently used in a majority of the vehicles produced in the United States. These vehicles generally employ three- and four-speed power transmissions. More recently, a trend towards more ratios, such as five- and six-speed power transmissions, has been proposed. In fact, some manufacturers do provide five-speed transmissions. Many of the vehicles utilizing manual type transmissions or countershaft type transmissions employ five- and six-speed power transmissions.
The five- and six-speed power transmissions provide improved vehicle acceleration performance and fuel economy when compared with three- and four-speed transmissions. Seven-speed transmissions offer further vehicle acceleration performance and fuel economy improvements over five- and six-speed transmissions. However, seven-speed power transmissions have not been proposed due to the complexity of these assemblies, as well as size and cost. There are many current patents that describe five- and six-speed power transmissions. Some of the six-speed power transmission patents, especially those assigned to the assignee of the present invention, describe six-speed power transmissions in families, wherein one or more family members incorporate a seven-speed power transmission.
It is an object of this invention to provide an improved family of transmissions providing at least seven forward speeds and one reverse speed.
In one aspect of the present invention, each family member has three planetary gearsets and each planetary gearset has three members comprised of a sun gear member, a ring gear member, and a planet carrier assembly member.
In another aspect of the present invention, each family member includes an interconnecting member connecting a first member of the first planetary gearset with a first member of the second planetary gearset, and with a first member of the third planetary gearset.
In yet another aspect of the present invention, each family member includes a transmission output shaft, which is continuously connected with at least one member of one of the planetary gearsets.
In yet still another aspect of the present invention, each family member includes an input shaft that is not continuously connected with any of the planetary gearsets but rather interconnected therewith through selectively engageable torque-transmitting mechanisms.
In still another aspect of the present invention, each family member includes six selectively engageable torque-transmitting mechanisms that are engaged in combinations of four to provide at least seven forward speed ratios and one reverse speed ratio in the planetary gearsets.
In a further aspect of the present invention, a first of the torque-transmitting mechanisms selectively interconnects the input shaft with a member of one of the planetary gearsets.
In a yet further aspect of the present invention, a second torque-transmitting mechanism selectively interconnects the input shaft with another member of one of the planetary gearsets.
In a still further aspect of the present invention, a third of the torque-transmitting mechanisms selectively interconnects at least one member of one of the planetary gearsets with another member of one of the planetary gearsets.
In a yet still further aspect of the present invention, a fourth of the torque-transmitting mechanisms selectively interconnects a member of the second or third planetary gearset with another member of one of the planetary gearsets.
In a further aspect of the present invention, a fifth of the torque-transmitting mechanisms selectively interconnects at least one member of one of the planetary gearsets with a transmission housing.
In another aspect of the present invention, a sixth of the torque-transmitting mechanisms selectively interconnects a transmission housing with another member of one of the planetary gearsets.